Direct sequence spread spectrum (DSSS) networks are used in implementing over the air systems. In one example, a smart utility network (SUN) is a low rate (5 kb/s to 1 Mb/s), low power, wireless communications technology that is specifically designed to be used in utility metering applications, such as for transmitting electric, gas, or water usage data from the one or more meters on the customer premises to a data collection point operated for the utility. The data collection point can then be connected to a central office for the utility by a similar or a different interface, which can be a high speed “backhaul” such as an optical fiber, copper wire, or other high speed wired connection to a network including the central office.
Different physical layers (PHYs) can be used for communication in over the air networks such as a SUN, including frequency shift keying (FSK), DSSS, and orthogonal frequency division multiplexing (OFDM). In an example, the devices that are allowed into the network of a closed DSSS communications system can be controlled by the utility or the network operator. Note that while some of the examples discussed herein for illustration include the operation of smart utility networks, the arrangements disclosed as aspects of the present application are not so limited and can be applied and used in conjunction with DSSS communications networks, generally.
A relevant standard has been promulgated by the IEEE, referred to as IEEE standard number 802.15.4g, entitled “Low-Rate Wireless Personal Area Networks (LR-WPANs)” issued Apr. 27, 2012 by the IEEE Computer Society and sponsored by the LAN/MAN Standards Committee. This standard identifies the PHY specifications for low data rate, wireless, SUN. The standard is intended to provide a globally used standard that facilitates very large scale process control applications such as a utility smart-grid network that are capable of supporting large, geographically diverse networks with minimal infrastructure and containing potentially millions of fixed endpoints. Note that arrangements of the present application is not limited to particular environment, including the SUN applications, but the various arrangements that form aspects of the present application are applicable to such applications.
In DSSS communications, data is transmitted utilizing packets. In packetized communication systems, packet arrival instants are generally random and unknown at the receiver. The payload can be successfully demodulated provided the receiver has symbol timing, frequency and phase offset information, in addition to achieving frame synchronization. In many practical applications, these parameters are not known a priori at the receiver and hence must be estimated from the received signal.